A fluid compression system (e.g., a chiller unit as part of an HVACR system), typically includes a compressor, a condenser, an evaporator and an expansion device forming a refrigeration circuit. The evaporator may be a flooded or falling-film evaporator, which often has a construction of a tube bundle within a shell. Such evaporators are typically used in fluid compression systems to cool a process fluid (e.g., water) flowing in the tube bundle which, in turn, is typically used in connection with a heat exchanger coil or air-handling unit to cool air moving through the coil or air-handling unit. The tube bundle is often stacked up from a bottom of the evaporator. In a flooded evaporator, the tube bundle is covered with working fluid, such as refrigerant, in the shell to help maximize heat exchange between the refrigerant and the process fluid.
The compressor of the fluid compression system often requires lubricant, such as oil, to lubricate moving parts of the compressor. In the fluid compression system, the lubricant may circulate in the refrigeration circuit along with the refrigerant, and then return to the compressor.